The clinical consequences of tissue injury and repair are determined by the tissue's ability to function. The function of musculoskeletal tissues is primarily mechanical: they support and distribute loads, provide motion, and dissipate energy in response to loading encountered during the activities of daily living. The structure and composition of these tissues are tailored to meet these demanding functions. With injury, the structure, composition, and mechanical function of the tissue break down. The goal of repairs is to restore the structure, composition, and mechanical function. Musculoskeletal tissues function under large and multidirectional loads, and they do so via a complex set of tissue mechanical behaviors that are anisotropic, viscoelastic, nonlinear, and inhomogeneous. Musculoskeletal tissues each have unique collagen architecture within an extrafibrillar matrix, and encompass a wide array of compositional and structural variety with respect to collagen and proteoglycan types, as well as other extracellular matrix constituents. As musculoskeletal treatments become more sophisticated, as our understanding of molecular biologic mechanisms become deeper, as genetically-engineered mice and rats are developed to ask questions never before possible, and as our imaging technologies advance, we must similarly be innovative in our understanding and quantification of tissue mechanical function and structural organization. The overall objective of this Structure Function Biomechanics Core is to develop and utilize a wide range of functional mechanical and structural assays of musculoskeletal tissue injury and repair, and to provide training and funding for new projects and collaborations utilizing these assays. The Specific Aims are: Aim 1: To provide guidance and training on the capabilities, advantages, and disadvantages of the various methodologies to assess musculoskeletal tissue biomechanical function and structure through formal educational enrichment programs and one-on-one interactions;Aim 2: To provide expertise and service for biomechanical function assays of musculoskeletal tissues;Aim 3: To provide expertise and service for structural assays of musculoskeletal tissues;and Aim 4: To provide funding for development of new projects and collaborations and to develop preliminary and/or feasibility data for investigators. Successful completion of these aims will significantly enhance the environment and the capabilities of researchers at the University of Pennsylvania, leading to new approaches to address musculoskeletal disorders and new collaborations between Core faculty who may have not previously included mechanical function and structural organization in their musculoskeletal research programs.